In Florida Keys, researchers investigate fish 'spinning and whirling' before dying
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The smalltooth sawfish was the first marine fish to receive federal protection as an endangered species under the Endangered Species Act in 2003. They were historically found in coastal waters from Texas to North Carolina, but now generally only found in Florida. (Credit: Dana Bethea/NOAA Fisheries)
March 29 (UPI) -- Scientists in the Florida Keys are scrambling to find out the cause of dozens of fish species spinning in the water and dying.
Hundreds of fish, including the endangered smalltooth sawfish, have been observed "spinning and whirling" in the Florida Keys, in what the Florida Fish and Wildlife Commission has labeled an "abnormal fish behavior event."
The Bonefish & Tarpon Trust has received 57 reports of this behavior since it was first observed in October.
BTT biologist Ross Boucek said 25 research mission have been conducted since mid-January, yielding 150 fish samples. The reports covered 35 different species of fish, including sharks and rays.
"Whatever this is, it does not discriminate based on species size, migratory pathways or behavior," Boucek said.
The casualties that have researchers the most concerned are the 28 confirmed smalltooth sawfish fatalities. The critically endangered fish has had its population decimated by fishery bycatches and coastal development and now is threatened by this unidentified killer.
The FWC has sent 52 fish, including 12 sawfish samples, to the University of South Alabama for analyses.
The smalltooth sawfish became the first protected marine fish under the Endangered Species Act in 2003.
Florida Gulf Coast University Professor Mike Parsons in an interview with CNN said his team has failed to turn up evidence for the most likely suspects of mass fish death, which include dissolved oxygen and red tide toxins.
The Water School at Florida Gulf Coast University is working with the FWC, the Florida Department of Environmental Protection and other agencies to determine the cause of the phenomenon.
Spinning fish in some cases recovered when moved to clean water, suggesting whatever is causing the behavior is in the water column and crossing the affected fish's gills.
A likely suspect is a naturally occurring toxin produced by an algae called Gambierdiscus. Researchers detected elevated levels of it in areas with affected fish, as well as in the gut contents of some affected fish.
The toxin is commonly found to accumulate on fish in coral reefs where the algae is found, It is not typically dangerous to the fish, but can be dangerous and even lethal to humans.
Parsons said its presence was "anywhere from five times higher to about 30 times above averages we've seen over the past 10 years."
"The maximum numbers we saw were below 10,000 cells per liter of water," he said. "That (number) is a lot for Gambierdiscus, but it's not a lot in terms of our typical blooming species. So that's one reason why Gambierdiscus was kind of under the radar here."
The link between Gambierdiscus and the spinning fish has not yet been proven, but scientists are chasing it as their strongest lead.
The BTT and FWC recommend people avoid eating fish harvested from areas where affected fish have been observed and to avoid swimming in areas with dead and symptomatic fish.
The FWC last week said on X that it launched a new event response website, which will be updated weekly with the most current information on the issue.
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